Battery and method for manufacturing the same

ABSTRACT

A battery having a collecting structure that can reduce internal resistance of the battery and a structure that allows easy manufacturing of the battery by the following processes is provided. An enlarged portion is formed near an opening end of a battery case and a supporting ledge is provided on the inner surface of the lower end of the enlarged portion. A collector of one polarity is bonded to an electrode plate group. A connection lead is bonded to the collector at one end and is bonded to a lower surface of a sealing member at the other end. An insulation gasket is mounted to a peripheral edge portion of the sealing member from a side opposite to the collector. The peripheral edge portion of the sealing member is supported by the supporting ledge with the insulation gasket interposed therebetween. Then, the peripheral edge portion of the sealing member is horizontally fastened and securely held via the insulation gasket by caulking the opening end of the battery case and performing a process for reducing the diameter of the enlarged portion.

The present application is a Divisional application of pending U.S.patent application Ser. No. 10/923,949, filed on Aug. 24, 2004, whichclaims the benefit of Japanese Patent Application Nos. 2003-304051,filed on Aug. 28, 2003; 2003-362872, filed on Oct. 23, 2003; and2004-047469, filed on Feb. 24, 2004, the contents of which are expresslyincorporated herein by reference in their entireties.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a battery having a collecting structureand a sealing structure that are novel and allow increase of output andcapacity, and a method for manufacturing such battery in a suitablemanner.

2. Description of the Related Art

In recent years, it has been advanced rapidly to make electronic devicessuch as audio-video equipment and a personal computer or mobilecommunication equipment portable and/or cordless. As a driving powersource of these electronic devices, an aqueous battery such as anickel-cadmium battery or nickel metal hydride battery was typicallyused conventionally. However, the aqueous battery has been recentlyreplaced with a non-aqueous electrolyte battery that can be chargedquickly and is high in both volume energy density and weight energydensity. As a typical non-aqueous electrolyte battery, a lithiumrechargeable battery is known. On the other hand, the nickel-cadmiumbattery and the nickel metal hydride battery mentioned above have beenspecialized in applications requiring large load characteristics, suchas a driving power source of a cordless power tool or an electricvehicle. Thus, the nickel-cadmium battery and the nickel metal hydridebattery are required to have larger current discharging characteristics.

As a conventional battery that can be used in large-current dischargingapplication, a battery having a structure shown in FIG. 19 is known.This battery (hereinafter, referred to as a first conventional battery)includes an electrode plate group 50 accommodated in a metal batterycase 51 that is a cylinder having a bottom. The electrode plate group 50includes a strip-shaped positive electrode plate and a strip-shapednegative electrode plate (both not shown) that are overlapped with aseparator (not shown) interposed therebetween and are wound spirally. Astructure for collecting an output from and an input to the positive andnegative electrode plates is formed as follows, here the structure beingsuitable for large-current discharge. The electrode plate group 50 isarranged in such a manner that an end (not shown) of the positiveelectrode plate protrudes above the electrode plate group 50 and an end(not shown) of the negative electrode plate protrudes below theelectrode plate group 50. To the end of the positive electrode plate, asubstantially circular disk-like positive collector 52 is welded at aplurality of positions. To that positive collector 52, one end 53 a of apositive lead 53 is welded by resistance welding. The other end 53 b ofthe positive lead 53 is welded to a filter portion 57 of a sealingmember 54 by resistance welding. Furthermore, a negative collector (notshown) is welded to the end of the negative electrode plate byresistance welding, and a negative collecting piece (not shown) of thenegative collector, which is like a tongue shape, is welded to thebottom of the battery case 51 by resistance welding.

The sealing member 54 includes the filter portion 57, a cap-shapedpositive terminal 58 and a safety vent body 59 interposed between thefilter portion 57 and the positive terminal 58, all of which areintegrated to form one unit. In the sealing member 54, the safety ventbody 59, while being compressed, closes a vent opening 57 a of thefilter portion 57. When a pressure inside the battery has reached orexceeded a set pressure that is set by the safety vent body 59, thesafety vent body 59 changes its shape so as to open the vent opening 57a, thereby allowing gas to escape to the outside through the ventopening 57 a to decrease its internal pressure. Then, the shape of thesafety vent body 59 returns to its original shape, thereby closing thevent opening 57 a.

In an outer circumferential surface of the battery case 51, an annulargroove 51 a is provided. The annular groove 51 a forms an annularsupporting portion 51 b in such a manner that the supporting portion 51b bulges inward. The sealing member 54 is supported by the supportingportion 51 b with an insulation gasket 60 interposed therebetween. Inaddition, the peripheral edge portion of the filter portion 57 is heldand secured by upper and lower opening edge portions of the battery case51, that have been caulked inward, from above and beneath, with theinsulation gasket 60 interposed therebetween, so that the sealing member54 is secured. Moreover, a ring-like upper insulation plate 61 isprovided between the upper end of the peripheral edge portion of theelectrode plate group 50 and the lower surface of the annular supportingportion 51 b. This ring-like upper insulation plate 61 secures theelectrode plate group 50 within the battery case 51 so as not to allowany movement of the electrode plate group 50 and also preventsshort-circuit between the electrode plate group 50 and the annularsupporting portion 51 b that may occur when they come into contact witheach other.

In the above battery, the positive lead 53 is bent at two positions tohave a substantially Z-shape when seen from the side thereof, in orderto prevent short-circuit between the positive lead 53 and the annularsupporting portion 51 b of the battery case 51 that may occur when thepositive lead 53 comes into contact with the annular supporting portion51 b. Aside from this, a battery shown in FIG. 20 (hereinafter, referredto as a second conventional battery) includes the positive lead 53 thatis bent at one position. In FIG. 20, the components that are the same asor similar to those in FIG. 19 are labeled with the same referencenumerals, and the redundant description is omitted.

The second conventional battery is fabricated in the following assemblyprocesses. As shown in FIGS. 21A and 21B, the electrode plate group 50is inserted into the battery case 51 and thereafter the positivecollector 52 and the negative collector (not shown) are welded to thepositive and negative electrode plates, respectively. Then, thering-like upper insulation plate 61 is inserted into the battery case 51and is placed on the positive collector 52. Subsequently, the annulargroove 51 a is formed at a predetermined portion on the outercircumferential surface of the battery case 51. Then, a predeterminedportion 53 a at one end of the positive lead 53 is welded to a portionof the positive collector 52 that is located on one side (on right sidein FIG. 21A) of a central gap of the electrode plate group 50. Then, thepositive lead 53 is bent at a portion near the welded portionperpendicularly and upward, so that the positive lead 53 stands to havea substantially L-shape and protrudes from the opening of the batterycase 51. Thereafter, the filter portion 57 of the sealing member 54 thathas been assembled in advance is welded to a predetermined portion 53 bat the other end of the positive lead 53. The reason why the positivelead 53 is bent to stand up above the central portion of the electrodeplate group 50 is to achieve smooth insertion of the sealing member 54into the opening of the battery case 51 having the annular supportingportion 51 b without bringing the lower end of the filter portion 57 ofthe sealing member 54 into contact with the annular supporting portion51 b.

Subsequently, the positive lead 53 is bent to be curved so as to rotatethe sealing member 54 as shown with an arrow in FIG. 21A, therebyarranging the sealing member 54 in a relative arrangement that enablesinsertion of the sealing member 54 into the opening of the battery case51. Then, the sealing member 54 is inserted into the battery case 51 andthe peripheral edge of the filter portion 57 of the sealing member 54 isplaced on the annular supporting portion 51 b of the battery case 51with the insulation gasket 60 interposed therebetween. At this time, theother end 53 b of the positive lead 53 is arranged above the gap of thecenter of the electrode plate group 50. In this state, an opening edgeportion of the battery case 51 is caulked inward. Thus, the opening edgeportion compresses the insulation gasket 60, so that the peripheral edgeportion of the filter portion 57 is held securely.

In most conventional batteries, the opening of the battery case 51 issealed with the sealing member 54, as shown in FIG. 19, and thereafter apressure is applied to the battery case 51 in a direction along the axisof the battery case 51 (vertical direction of the battery case 51) so asto press the sealing member 54 down toward the inside of the batterycase 51 while flattening out the annular groove 51 a. As a result, thesealing member 54 securely presses the electrode plate 50 by means ofthe upper insulation plate 61 with the positive lead 53 interposedtherebetween. During this application of the pressure, the positive lead53 is deformed so as to be folded. However, the vent opening 57 a of thesealing member 54 may be closed by a portion of the positive lead 53,which is located at the center of the electrode plate group 50, becauseof variation of the position of the positive lead 53 at which thepositive lead 53 is welded to the filter portion 57.

In order to overcome the above drawback, other batteries have beenconventionally proposed. One of those batteries has a positive leadportion formed integrally with a positive collector portion with afolded portion positioned in therebetween. In this battery (hereinafterreferred to as a third conventional battery), the conventional positivecollector and positive lead are formed integrally with each other. Thepositive lead portion has a horseshoe shape with a U-shaped notch thatis to fit into a ring-like projection projecting from the vent openingof the sealing member. See Japanese Utility Model Laid-Open PublicationNo. Sho 58-74768, for example.

Moreover, still another conventional battery (hereinafter, referred toas a fourth conventional battery) is fabricated in a process shown inFIG. 22 (see Japanese Patent Laid-Open Publication No. 2001-155712, forexample). More specifically, the positive lead 53 is welded to asubstantially central portion of the positive collector 52 at its oneend 53 a. Then, the positive lead 53 is bent upward at a portion nearthe welded portion perpendicularly so as to stand like an L-shape and ispositioned in such a manner that a gas escape hole 53 d provided at itsother end portion is in agreement with the vent opening 57 a of thefilter portion 57 of the sealing member 54. In this state, portions 53 band 53 c near the gas escape hole 53 d are welded to the filter portion57. Subsequently, the sealing member 54 is inserted into the opening ofthe battery case 51 while the positive lead 53 is bent, and is thenplaced on the annular supporting portion 51 b with the insulation gasket60 therebetween. Finally, the opening of the battery case 51 is caulkedtoward the inside of the battery case 51. Please note that thecomponents in FIG. 22 that are the same as or similar to those in FIGS.21A and 21B are labeled with the same reference numerals in order toomit the redundant description.

Moreover, still another battery assembled in a process shown in FIG. 23has been conventionally proposed, as described in Japanese PatentLaid-Open Publication No. 2001-256935, for example. In FIG. 23, thecomponents that are the same as or similar to those in FIG. 21A arelabeled with the same reference numerals. This battery (hereinafter,referred to as a fifth conventional battery) is fabricated as follows.In welding of the positive lead 53 and the sealing member 54, firstly,one end of the positive lead 53 is welded to the peripheral end portionof the positive collector 52. Then, the filter portion 57 of the sealingmember 54 arranged vertically above that welded portion of the positivelead 53 is welded to the other end of the positive lead 53. The sealingmember 54 is then inserted into the opening of the battery case 51 whilebeing rotated as shown with an arrow in FIG. 23 so as to be arrangedhorizontally. In this battery, one end of the positive lead 53 is weldedto the peripheral end portion of the positive collector 52. Thus, thepositive lead 53 does not exist above the gap at the center of theelectrode plate group 50 when the annular groove (not shown) isflattened out after the sealing member 54 closed the opening of thebatter case 51. Therefore, the vent opening 57 a of the filter portion57 cannot be closed by the positive lead 53.

Attaching the sealing member 54 to the insulation gasket 60 is performedin accordance with a procedure shown in FIGS. 24A through 24C (seeJapanese Patent Laid-Open Publication No. Hei 6-267516, for example).More specifically, the sealing member 54 is inserted into the insulationgasket 60 at an angle, as shown in FIG. 24A, and one end of the filterportion 57 of the sealing member 54 is then brought into contact with abottom surface of the insulation gasket 60, as shown in FIG. 24B.Finally, the other end of the filter portion 57 placed on the upper endportion of the insulation gasket 60 is pressed down so as to causeslight deformation of the insulation gasket 60 to the outside and isfurther pressed down along the inner side face of the insulation gasket60. In this manner, the insertion of the sealing member 54 into theinsulation gasket 60 is performed.

However, in the first conventional battery, the positive lead 53 is bentto have a substantially Z-shape, as shown in FIG. 19. Thus, a collectingdistance increases as the length of the positive lead 53 increases. Inaddition, it is necessary to make the positive lead 53 in the firstconventional battery thinner because the positive lead 53 has to be benttwice. This increases the internal resistance of the battery and acts asa factor of disturbing large-current discharge characteristics.Moreover, the welded portions of the long thin positive lead 53 and thesealing member 54 may come off when the battery receives strong impactor vibration and the electrode plate 50 is moved. This decreasesvibration resistance or impact resistance of the battery.

The second conventional battery has an advantage that the length of thepositive lead 53 can be made slightly shorter, as compared with thefirst conventional battery. However, since there is the annularsupporting portion 51 b for pressing the electrode plate group 50 andsupporting the sealing member 54, and the filter portion 57 of thesealing member 54 and the upper end of the electrode plate group 50 arearranged above and below the annular supporting portion 51 b,respectively, the filter portion 57 and the upper end of the electrodeplate group 50 are arranged away from each other by a relatively largedistance. Thus, the positive lead 53 has to have the lengthcorresponding to the above large distance. This prevents the reductionof the internal resistance of the battery and the improvement of thelarge-current discharging characteristics. Moreover, in the secondconventional battery, the sealing member 54 has to be arranged at thecentral portion of the battery case 51, as shown in FIG. 21A, when beingbonded to the positive lead 53 that is bent to be L-shaped and thuserected. Thus, when electrolyte is injected into the battery case 51after the bonding of the sealing member 54 to the positive lead 53, itis necessary to bend the positive lead 53 to the right from the stateshown in FIG. 21A so as to move the sealing member 54 away from the gasescape hole 52 a of the positive collector 52, then move the positivelead 53 back to the state shown in FIG. 21A after the injection of theelectrolyte, and finally rotate the sealing member 54 in the directionshown with the arrow in FIG. 21A. Therefore, the increase of number ofunnecessary work decreases productivity.

The third conventional battery also has problems mentioned below. Whenthe horseshoe-shaped notch of the positive lead portion is positioned atthe ring-like projection of the sealing member, secure positioningcannot be achieved unless the innermost portion of the notch is broughtinto contact with the ring-like projection. During the positioning, evena small misalignment causes variations of positions at which spotwelding is performed or defective welding. Moreover, since the positivelead has a horseshoe shape, welded portions of spot welding directlyreceive load when vibration is applied to the battery. Thus, the weldedportions may come off easily.

In the fourth conventional battery, welding of the positive lead 53 andthe sealing member 54 to each other is performed while the sealingmember 54 is displaced from the center of the battery case 51 toward theside of bending of the positive lead 53. Thus, there is an advantagethat electrolyte can be injected without moving the sealing member 54after the welding of the positive lead 53 and the sealing member 54.However, since the fourth conventional battery also has the annulargroove 51 a in the battery case 51, the filter portion 57 of the sealingmember 54 and the upper end of the electrode plate group 50, that arearranged above and below the annular supporting portion 51 b,respectively, are away from each other by a relatively large distance.Thus, the positive lead 53 has to have a length corresponding to theabove large distance, preventing reduction of the internal resistance ofthe battery.

Furthermore, in the fifth conventional battery, the peripheral edgeportion of the sealing member 54 inevitably comes into contact with theedge of the opening of the battery case 51. Therefore, it is hard to putthe fifth conventional battery into practical use.

SUMMARY OF THE INVENTION

Therefore, the present invention was made in view of the drawbacks ofthe aforementioned conventional techniques, and it is an object of thepresent invention to provide a battery that has a collecting structureenabling reduction of internal resistance of the battery and isfabricated easily, and a manufacturing method that suitably fabricatesthe battery with improved productivity.

In order to achieve the above object, a battery of the present inventionincludes a cylindrical metal battery case having a bottom and anelectrode plate group accommodated in the battery case. The electrodeplate group includes a strip-shaped positive electrode plate and astrip-shaped negative electrode plate that are spirally wound with aseparator interposed therebetween. An opening at an upper end of thebattery case is sealed by a sealing member with an insulation gasketinterposed therebetween. The battery case has an enlarged portion formedabove an upper end of the electrode plate group. Please note that theupper end of the electrode plate group is an end thereof on the sideclose to an opening end of the battery case. The battery case furtherhas an annular supporting ledge formed on an inner surface of a lowerend of the enlarged portion. A collector having one polarity is bondedto an end of the electrode plate having the one polarity that projectsupward from the electrode plate group. To the collector of the onepolarity, one end of a connection lead is bonded in an arrangement inwhich a notch formed at the one end of the connection lead is inagreement with a part of a hole edge of an electrolyte-injection hole atthe center of the collector of the one polarity. Moreover, the other endof the connection lead, which is a tip end of a folded portion extendingfrom the one end, is bonded to a portion of the sealing member, theportion being displaced from a vent opening at the center of the sealingmember toward the folded portion of the connection lead. A peripheraledge portion of the sealing member is supported by the supporting ledgewith the insulation gasket interposed therebetween, and is fastened in ahorizontal direction with the insulation gasket interposed therebetweenby performing caulking of the opening end of the battery case inward andreducing a diameter of the enlarged portion.

According to this battery, since the enlarged portion is provided nearthe opening end of the battery case and the supporting ledge forsupporting the peripheral edge portion of the sealing member is formedon the inner surface of the lower end of the enlarged portion, anannular supporting portion formed by an annular groove in theconventional battery is eliminated. Thus, the electrode plate groupfurther extends toward the opening end of the battery case by a lengthprovided by omission of the conventional annular supporting portion, sothat the upper end of the electrode plate group reaches a higher level.This greatly reduces a distance between the collector mounted to theupper end of the electrode plate group and the sealing member, ascompared with that in the conventional battery, and also reduces thelength of the connection lead for electrically connecting the collectorand the sealing member greatly. Therefore, a collecting distance isreduced by a distance corresponding to the reduction of length of theconnection lead, resulting in reduction of internal resistance of thebattery and increase of an output of the battery.

Moreover, according to this battery, the height of the electrode plategroup is increased by a volume corresponding to a useless space providedby inclusion of the annular supporting portion in the conventionalbattery, thereby increasing the volume of the electrode plate group.This increases the capacity of the battery. In addition, the connectionlead is made as short as possible and does not require a notch oropening for avoiding interference of the connection lead with the ventopening of the sealing member, at the other end thereof. Thus, theconnection lead has a simple rectangular shape and therefore is formedat a low cost. Furthermore, the connection lead will not close the ventopening even in a case where the connection lead is deformed and foldedby being compressed in a vertical direction.

A method for manufacturing a battery of the present invention includesthe steps of: accommodating a spiral electrode plate group in acylindrical battery case having a bottom, the battery case having anenlarged portion formed close to an opening end thereof and an annularsupporting ledge on an inner surface of a lower end of the enlargedportion, a collector of one polarity being bonded to an upper end of thespiral electrode plate group while a collector of another polarity isbonded to a lower end thereof; bonding one end of a connection lead tothe collector of the one polarity in an arrangement in which a notchformed at the one end of the connection lead is in agreement with a partof a hole edge of an electrolyte-injection hole at a center of thecollector of the one polarity, and then bending the connection lead at aportion near a portion bonded to the collector of the one polarity insuch a manner that the connection lead stands vertically; bondinganother end of the standing connection lead to a portion of a sealingmember arranged parallel to the other end of the standing connectionlead, the portion of the sealing member being below a vent openingpositioned at a center of the sealing member; injecting electrolyte intothe battery case through the electrolyte-injection hole of the collectorof the one polarity; rotating the sealing member while the connectionlead is bent to form a folded portion between the one end and the otherend thereof, thereby arranging the sealing member parallel to an openingsurface of the battery case to be opposed thereto, inserting the sealingmember thus arranged into the opening of the battery case, and latchinga peripheral edge portion of the sealing member on the supporting ledgeof the battery case with an insulation gasket interposed therebetween;and fastening the peripheral edge portion of the sealing member in ahorizontal direction with the insulation gasket interposed therebetweenby performing caulking of an opening end of the battery case inward andreducing a diameter of the enlarged portion.

According to this manufacturing method, the annular supporting portionis not used. Thus, even if the sealing member is welded to the other endof the connection lead standing at a position away from the center ofthe electrode plate group and is then rotated from this state to a statein which the sealing member is arranged parallel to the opening surfaceof the battery case while the connection lead is bent, the sealingmember never comes into contact with any portion of the battery caseduring the rotation and is placed in the predetermined state, althoughthe sealing member arranged vertically is mounted at the position awayfrom the center of the electrode plate group. Therefore, the sealingmember is inserted into the opening of the battery case suitably whilethe collector and the sealing member are electrically connected by meansof the short connection lead.

Moreover, in another battery of the present invention, the insulationgasket is mounted to the peripheral edge portion of the sealing memberfrom a side opposite to the collector of the one polarity. Theperipheral edge portion of the sealing member is supported by thesupporting ledge with the insulation gasket interposed therebetween andis fastened in the horizontal direction by performing caulking of theopening end of the battery case inward and reducing the diameter of theenlarged portion.

According to this battery, the volume of the electrode plate group isincreased by increasing the height of the electrode plate group by alength corresponding to a useless space formed by inclusion of theannular supporting portion in the conventional battery, thus increasingthe capacity of the battery. Moreover, since the insulation gasket ismounted to the peripheral edge portion of the sealing member from theside opposite to the collector, this mounting of the insulation gasketis performed in a state where the sealing member is connected to thecollector of one polarity with the connection lead interposedtherebetween. That is, it is not necessary to insert the sealing memberconnected to the connection lead into the battery case through theopening of the battery case while rotating the sealing member around afolding line of the connection lead as in the conventional battery.Thus, the length of the connection lead is further reduced and thethickness thereof is made relatively thick. In accordance with this,further reduction of the internal resistance of the battery and furtherincrease of the output thereof are achieved.

Another method for manufacturing a battery of the present inventioncomprises the steps of: bonding a collector of one polarity and acollector of another polarity to upper and lower ends of an electrodeplate group, respectively; bonding a connection base portion of aconnection lead to the collector of the one polarity before or after thebonding of the collector of the one polarity to the electrode plategroup; bonding a connected portion of the connection lead to a lowersurface of a peripheral edge portion of a filter portion of a sealingmember by resistance welding, the connected portion being formedcontinuously from the connection base portion with a standing portioninterposed therebetween; mounting an insulation gasket to the peripheraledge portion of the filter portion from a side opposite to thecollector; accommodating the electrode plate group in a cylindricalbattery case that has a bottom, and an enlarged portion close to anopening end and an annular supporting ledge formed on an inner surfaceof a lower end of the enlarged portion, and placing the peripheral edgeportion of the filter portion on the supporting ledge with theinsulation gasket interposed therebetween; caulking the opening end ofthe battery case inward and reducing a diameter of the enlarged portionto horizontally fasten and secure the peripheral edge portion of thesealing member with the insulation gasket interposed therebetween;injecting electrolyte into the battery case through anelectrolyte-injection hole of the collector of the one polarity; andassembling the sealing member by bonding a cap terminal to the filterportion with a safety vent body interposed therebetween.

According to this manufacturing method, the insulation gasket is mountedto the peripheral edge portion of the filter portion of the sealingmember after bonding of the filter portion to the connection lead bondedto the collector. Thus, the connection lead and the peripheral edgeportion of the filter portion of the sealing member are bonded to eachother by resistance welding because this bonding is performed before themounting of the insulation gasket and the insertion of the sealingmember into the battery case. Therefore, the resistance welding of thefilter portion of the sealing member and the connection lead isperformed stably with high precision, as compared with the conventionalbattery in which the sealing member is welded to the connection leadwhile being arranged vertically, thus providing excellent weldingstrength. This results in reduction of electric resistance at the weldedportion. Moreover, according to this battery manufacturing method, it isnot necessary to provide a folded portion in the connection lead. Thus,the connection lead can be further shortened.

While novel features of the invention are set forth in the preceding,the invention, both as to organization and content, can be furtherunderstood and appreciated, along with other objects and featuresthereof, from the following detailed description and examples when takenin conjunction with the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a vertical cross-sectional view of a battery according to afirst embodiment of the present invention;

FIGS. 2A and 2B are a plan view and a cross-sectional view of thebattery of the first embodiment, respectively, showing a relativearrangement of an electrode plate group, a positive collector, and apositive lead;

FIG. 3A is a cross-sectional view of the battery of the first embodimentduring a manufacturing process, and FIG. 3B is a right side view of thebattery shown in FIG. 3A;

FIG. 4 is a cross-sectional view of the battery of the first embodimentwhen bending of the positive lead starts from the state shown in FIGS.3A and 3B;

FIGS. 5A and 5B are a plan view and a cross-sectional view of a batteryaccording to a second embodiment of the present invention, respectively,showing a relative arrangement of an electrode plate group, a positivecollector, and a positive lead;

FIG. 6 is a vertical cross-sectional view of a battery according to athird embodiment of the present invention;

FIGS. 7A and 7B are a plan view and a cross-sectional view of thebattery of the third embodiment of the present invention, respectively,showing a relative arrangement of an electrode plate group, a positivecollector, and a positive lead;

FIGS. 8A and 8B are a plan view and a vertical cross-sectional view ofan insulation gasket in the battery of the third embodiment, FIG. 8C isan enlarged view of a part of FIG. 8B, and FIG. 8D is an enlarged viewof a part of FIG. 8B while a sealing member is attached;

FIG. 9A is a cross-sectional view of the battery of the thirdembodiment, showing a relative arrangement of respective partscorresponding to an assembly procedure, and FIG. 9B is a cross-sectionalview of that battery while the positive and negative collectors and thepositive lead are mounted to the electrode plate group;

FIGS. 10A, 10B, and 10C are cross-sectional views of the battery of thethird embodiment, showing a process of attaching a filter portion of thesealing member, a process of attaching the insulation gasket, and aprocess of welding of the positive collector to a battery case afterinsertion of the electrode plate group into the battery case,respectively;

FIGS. 11A and 11B are cross-sectional views of the battery of the thirdembodiment, showing a preliminary sealing process and an electrolyteinjection process, and a regular sealing process, respectively;

FIGS. 12A and 12B are a plan view and a cross-sectional view,respectively, showing a manufacturing process as an alternative of themanufacturing process shown in FIG. 9B;

FIG. 13 is a vertical cross-sectional view of a sealing portion of abattery according to a fourth embodiment of the present invention;

FIGS. 14A and 14B are a plan view and a cross-sectional view of thebattery of the fourth embodiment, respectively, showing a relativearrangement of a positive collector and a positive lead, and FIG. 14C isa cross-sectional view of that battery when a manufacturing processsimilar to the process shown in FIG. 7B is used;

FIG. 15A is a partial cross-sectional view of another exemplaryinsulation gasket of the present invention, and FIG. 15B is across-sectional view showing a state where a peripheral edge portion ofa filter portion of a sealing member is held and secured by an openingend of a battery case that has been caulked toward the inside of thebattery case, with the insulation gasket interposed therebetween;

FIGS. 16A and 16B are a plan view and a cross-sectional view of stillanother exemplary insulation gasket of the present invention,respectively, and FIG. 16C is an enlarged view of a part of FIG. 16B;

FIG. 17A is a partially broken cross-sectional view of still anotherexemplary insulation gasket of the present invention, and FIG. 17B is apartially broken cross-sectional view showing a state where theperipheral edge portion of the filter portion of the sealing member isheld and secured by the opening end of the battery case that has beencaulked toward the inside of the battery case, with that insulationgasket interposed therebetween;

FIGS. 18A through 18G are cross-sectional views sequentially showingmanufacturing processes of the battery using the insulation gasket shownin FIGS. 17A and 17B;

FIG. 19 is a cross-sectional view of a sealing portion of a conventionalbattery;

FIG. 20 is a cross-sectional view of a sealing portion of anotherconventional battery;

FIGS. 21A and 21B are a cross-sectional view and a right side viewshowing a manufacturing process of the battery shown in FIG. 19,respectively;

FIG. 22 is a cross-sectional view showing a manufacturing process ofstill another conventional battery;

FIG. 23 is a cross-sectional view showing a manufacturing process ofstill another conventional battery; and

FIGS. 24A through 24C are cross-sectional views sequentially showingtypical processes for attaching a sealing member to an insulation gasketin the conventional battery.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiment of the present invention will now be describedbelow with reference to the accompanying drawings. It should be notedthat the embodiments described below do not intend to limit the scope ofthe present invention, but exemplify the invention.

FIG. 1 is a vertical cross-sectional view of a battery according to afirst embodiment of the present invention. This battery includes acylindrical metal battery case 1 having a bottom; an electrode plategroup 2 in which a strip-shaped positive electrode plate 3 and astrip-shaped negative electrode plate 4 are spirally wound with aseparator 7 interposed therebetween; and a sealing member 8 thatair-tightly closes an opening of the battery case 1 with an insulationgasket 12 interposed therebetween. The electrode plate group 2 isaccommodated in the battery case 1 and forms together with electrolyte(not shown) an electric-power generation component.

The electrode plate group 2 is arranged in such a manner that one end 3a of the positive electrode plate 3 projects upward from the electrodeplate group 2 while one end 4 a of the negative electrode plate 4projects downward from the electrode plate group 2. A negative collector9 having a circular disk-like shape is welded to the end 4 a of thenegative electrode plate 4. Between the negative collector 9 and thebottom of the battery case 1 is inserted an elastic electric conductor10 that is formed by a ring of foamed metal. This elastic electricconductor 10 absorbs variations in height of the electrode plate group 2and contributes to vibration resistance and impact resistance of thebattery. The negative collector 9 has a notch provided at its centralportion, and a tongue-like negative collecting piece 9 a is formed byraising a part of the negative collector 9 via that notch and orientingit downward. The negative collecting piece 9 a is welded to the bottomsurface of the battery case 1 by resistance welding. On the other hand,to the end 3 a of the positive electrode plate 3, a positive collector11 is welded by resistance welding.

The battery case 1 has an enlarged portion 1 a, that has a slightlylarger diameter than the cylindrical portion for accommodating theelectrode plate group 2, near the opening and also has an annularsupporting ledge 1 b on the inner surface of the battery case 1 betweenthe enlarged portion 1 a and the cylindrical portion. The enlargedportion 1 a is formed at a slightly higher level than the upper end ofthe electrode plate group 2 accommodated in the cylindrical portion ofthe battery case 1.

The sealing member 8 includes a filter portion 21 having a vent opening21 a for allowing gas generated inside the battery to escape, acap-shaped positive terminal 22 that overlaps the filter portion 21 andis secured, and a safety vent body 23 made of rubber that is held andsecured between the filter portion 21 and the cap-shaped positiveterminal 22 and closes the vent opening 21 a. While being caught on thesupporting ledge 1 b of the battery case 1 with an insulation gasket 12interposed therebetween, a peripheral edge portion of the filter portion21 is securely held by the enlarged portion 1 a that has been caulkedinward and processed to have a reduced diameter with the insulationgasket 12 interposed therebetween in such a manner that the peripheraledge of the filter portion 21 is fastened vertically and horizontally.The insulation gasket 12 made of resin has a supporting bottom surface12 a on which the peripheral edge portion of the filter portion 21 ofthe sealing member 8 is placed.

FIG. 2A is a plan view showing a relative arrangement of the electrodeplate group 2, the positive collector 11, and a positive lead 17. FIG.2B is a cross-sectional view of a portion corresponding to FIG. 2A. Thepositive collector 11 is formed by an electrically conductive platehaving a substantially rectangular shape that is accommodated in thecross-sectional shape of the electrode plate group 2, and has a circularelectrolyte-injection hole 13 at its center, corresponding to a centralgap of the electrode plate group 2. The positive collector 11 also hasfour openings 14 which are formed by cut portions extending from fourcorners of the rectangular positive collector 11 to positions near thecenter thereof, respectively. Furthermore, burring projections 18 athrough 18 d are formed integrally with the positive collector 11. Theburring projections 18 a through 18 d are formed by bending sides of therespective openings 14 downward and perpendicularly. The positivecollector 11 is welded to the positive electrode plate 3 by resistancewelding while eight burring projections 18 a through 18 d intersect withthe end 3 a of the positive electrode plate 3 and partially bite intothe end 3 a.

Next, the positive lead 17 for electrically connecting the positivecollector 11 and the filter portion 21 of the sealing member 8 will bedescribed with reference to FIGS. 3A, 3B, and 4. FIG. 3A is across-sectional view showing a manufacturing process in which thesealing member 8 is welded to one end of the positive lead 17 bonded tothe positive collector 11 at the other end, FIG. 3B is a right side viewof FIG. 3A, and FIG. 4 is a cross-sectional view showing a state whenbending of the positive lead 17 has started from the state shown inFIGS. 3A and 3B. It should be noted that, in order to clearly show awelded portion at which the positive lead 17 and the sealing member 8 iswelded, FIGS. 3A, 3B, and 4 illustrate the positive lead 17 and thesealing member 8 while they are away from each other for the sake ofconvenience. The positive lead 17 is a rectangular plate of electricallyconductive material, as shown in FIGS. 3A and 3B, and includes a notch19 at its one end to be connected to the positive collector 11. Thenotch 19 has a semi-circular shape corresponding to theelectrolyte-injection hole 13 of the positive collector 11, as shown inFIG. 2A.

The positive lead 17 is placed so that the notch 19 formed on that endserving as a connection base portion is in agreement with a hole edge ofthe electrolyte-injection hole 13 positioned at the center of theelectrode plate group 2, in such a manner that one end thereof overlapthe positive collector 11. The positive lead 17 is bonded to thepositive collector 11 by resistance welding at portions on both sides ofthe notch 19 at the one end. Then, the positive lead 17 is bent upwardand perpendicularly at a portion near two welded portions 17 a and 17 bat the one end, so that an intermediate lead portion of the positivelead 17 stands vertically. The other end of the positive lead 17, i.e.,a connected portion, is placed to overlap a portion of the filterportion 21 near the vent opening 21 a of the filter portion 21 of thesealing member 8 and is bonded to the filter portion 21 by resistancewelding.

Subsequently, as shown in FIG. 4, the positive lead 17 is bent at aportion near the welded portion 17 c in the other end to rotate thesealing member 8 until the sealing member 8 is arranged parallel to theopening surface of the battery case 1. The sealing member 8 is insertedinto the opening of the battery case 1 while being kept parallel to theopening surface. Then, the sealing member 8 is caught on the supportingledge 1 b of the battery case 1 while the peripheral edge portion of thefilter portion 21 of the sealing member 8 engages with the supportingbottom surface 12 a of the insulation gasket 12, and thereafter theopening end of the battery case 1 is caulked inward. Finally, theenlarged portion 1 a of the battery case 1 is processed to have areduced diameter. This enlarged portion 1 a with the reduced diameterfastens the filter portion 21 in the horizontal direction.

In this battery, the enlarged portion 1 a is provided near the openingend of the battery case 1 and the supporting ledge 1 b for supportingthe filter portion 21 of the sealing member 8 is formed on the innersurface of the lower end of the enlarged portion 1 a, therebyeliminating the use of the annular supporting portion 51 b formed by theannular groove 51 a in the conventional battery shown in FIG. 20. Whenthe annular supporting portion 51 b is not used, the ring-like upperinsulation plate 61 for preventing the contact between the annularsupporting portion 51 b and the electrode plate group 50 is alsounnecessary. Therefore, the supporting ledge 1 b of the battery case 1will be provided near the upper end of the electrode plate group 2accommodated in the battery case 1. In other words, according to thebattery of the present embodiment, the upper end of the electrode plategroup 2 extends higher toward the opening end of the battery case 1 bythe length corresponding to the conventional annular supporting portion51 b. Therefore, the distance between the positive collector 11 attachedto the upper end of the electrode plate group 2 and the filter portion21 of the sealing member 8 is largely shortened as compared with theconventional battery, as is apparent from comparison of FIG. 2B withFIGS. 19 and 20. Accordingly, the positive lead 17 for electricallyconnecting the positive collector 11 and the filter portion 21 islargely shortened.

As a result, the collecting distance in this battery is reduced by adistance corresponding to the reduction of the length of the positivelead 17, and therefore the battery reduces its internal resistancelargely so as to achieve higher output. Moreover, the volume of theelectrode plate group 2 is increased by increasing the height of theelectrode plate group 2 by the height corresponding to a useless spaceformed by the provision of the annular supporting portion 51 b in theconventional battery. This increase of the volume of the electrode plategroup 2 also increases the capacity of the battery.

In addition, in the battery of the present embodiment, the annularsupporting portion 51 b does not exist. Thus, even if the sealing member8 is welded to the other end of the positive lead 17 that is made tostand vertically at a position on one side (left side in FIG. 3A) of thecenter of the electrode plate group 2 as shown in FIG. 3A, and is thenrotated by bending the positive lead 17 until the sealing member 8 isarranged parallel to the opening of the battery case 1, the lower end ofthe sealing member 8 will not come into contact with any portion of thebattery case 1 although the sealing member 8 arranged vertically ismounted at a position displaced from the center of the electrode plategroup 2 toward one side. On the other hand, in the conventional battery,in order to rotate the sealing member 54 without contact between thelower end of the sealing member 54 and the annular supporting portion 51b, it was necessary to weld the sealing member 54 to the positive lead53 while the sealing member 54 was arranged vertically at a positioncorresponding to the center of the electrode plate group 50.

In this manner, the positive lead 17 is bonded to the positive collector11 in a relative arrangement in which one end of the positive lead 17 ispositioned to be displaced from the center of the electrode plate group2 toward one side, as shown in FIG. 3A, and is bonded to the filterportion 21 in a relative arrangement in which the other end is arrangedat a position below the vent opening 21 a of the sealing member 8 thatis arranged vertically, as shown in FIG. 3B. Thus, the length of thepositive lead 17 is reduced, and the shape of the positive lead 17becomes a simple rectangular shape because it is unnecessary to form anotch or opening at its other end in order to prevent interference withthe vent opening 21 a of the filter portion 21. This is advantageous toreduce the cost. Moreover, in the battery of the present embodiment, thepositive lead 17 will not close the vent opening 21 a, even if thepositive lead 17 is compressed in the vertical direction from the stateshown in FIG. 2B and is folded.

FIG. 5A is a plan view showing a relative arrangement of the electrodeplate 2, the positive collector 11, and the positive lead 17 in thebattery according to a second embodiment of the present invention. FIG.5B is a cross-sectional view corresponding to FIG. 5A. In FIGS. 5A and5B, the components that are the same as or similar to those in FIGS. 2Aand 2B are labeled with the same reference numerals and redundantdescription is omitted. Although the positive lead 17 shown in FIGS. 2Aand 2B has the semi-circular notch 19, the positive lead 17 of thebattery shown in FIGS. 5A and 5B has a circular hole 15 having aslightly smaller diameter than that of the electrolyte-injection hole 13of the positive collector 11. Moreover, in the positive lead 17 of thepresent embodiment, four welded portions 16 a through 16 d for weldingof the positive lead 17 to the positive collector 11 are provided atfour positions surrounding the circular hole 15, respectively. Inaddition, a pressing piece 12 b is formed integrally with the insulationgasket 12 in such a manner that the pressing piece 12 b extendsobliquely downward from the supporting bottom surface 12 a. Since thepressing piece 12 b is formed integrally with the insulation gasket 12,the elastic electric conductor 10 shown in FIG. 1 is not necessary, thusreducing the cost. Furthermore, since the pressing piece 12 b formedintegrally with the insulation gasket 12 securely holds the electrodeplate group 2 with the positive collector 11 interposed therebetween inthe battery of the present embodiment, vibration resistance and impactresistance are improved.

In a case of the positive lead 17 shown in FIGS. 2A and 2B, currentpaths between two welded portions 17 a and 17 b and the burringprojections 18 a and 18 b are short, whereas current paths between theother two burring projections 18 c and 18 d and the welded portions 17 cand 17 d are long. On the other hand, in the positive lead 17 of thebattery shown in FIGS. 5A and 5B, four welded portions 16 a through 16 dare provided for the four burring projections 18 a through 18 d,respectively. Thus, each of current paths between the welded portionsand the burring projections is short. Therefore, the internal resistanceof the battery is further reduced.

FIG. 6 is a vertical cross-sectional view of a battery according to athird embodiment of the present invention. In FIG. 6, the componentsthat are the same as or similar to those in FIG. 1 are labeled with thesame reference numerals, and redundant description will be omitted butonly differences between the structure shown in FIG. 6 and that shown inFIG. 1 will be described. In the third embodiment, shapes of aninsulation gasket 27 and a positive lead 20 are characteristic. Thedetails of the insulation gasket 27 and the positive lead 20 will bedescribed later. The negative collector 9 is formed by a disc springhaving an elastic connection portion 9 b that expands downward from acentral region of the disc-like negative collector 9. The elasticconnection portion 9 b is welded to the bottom of the battery case 1 byresistance welding. Due to the provision of the elastic connectionportion 9 b, the elastic electric conductor 10 shown in FIG. 1 iseliminated.

FIG. 7A is a plan view showing a relative arrangement of the electrodeplate group 2, the positive collector 11, and the positive lead 20. FIG.7B is a cross-sectional view of a portion corresponding to FIG. 7A. Thepositive collector 11 is formed by a plate of electrically conductivematerial having a substantially rectangular shape that is accommodatedwithin a cross-sectional shape of the electrode plate group 2, and has acircular electrolyte-injection hole 13 at its center, corresponding to acentral circular hole of the electrode plate group 2. The positivecollector 11 also has four openings 14 extending from four corners ofthe rectangular positive collector 11 to positions near the centerthereof, respectively. Furthermore, burring projections 18 a through 18d are formed integrally with the positive collector 11. The burringprojections 18 a through 18 d are formed by bending sides of therespective openings 14 downward and perpendicularly. The positivecollector 11 is welded to the positive electrode plate 3 by resistancewelding while four pairs of burring projections 18 a through 18 dintersect with the end 3 a of the positive electrode plate 3 andpartially bite into the end 3 a.

The positive lead 20 for electrically connecting the positive collector11 and the filter portion 21 of the sealing member 8 to each other ismade of a substantially rectangular conductive plate, and is bentperpendicularly at its two portions. As a result, in the positive lead20, a standing portion 20 b extends from a connection base portion 20 ato be welded to the positive collector 11 upward in a directionperpendicular to the connection base portion 20 a, and a connectedportion 20 c extends parallel to the connection base portion 20 a fromthe upper end of the standing portion 20 b toward the peripheral edge ofthe sealing member 8. The connected portion 20 c has two projections 24at two portions thereof and is welded to the lower surface of the filterportion 21 of the sealing member 8 with the projections 24 by resistancewelding.

FIGS. 8A and 8B are a plan view and a vertical cross-sectional view ofthe insulation gasket 27 in the battery shown in FIG. 6, respectively.FIG. 8C is an enlarged view of a part of FIG. 8B, and FIG. 8D is anenlarged view of a part of the insulation gasket 27 to which the filterportion 21 of the sealing member 8 has been attached. The insulationgasket 27 is a molded part made of synthetic resin, which is a shortcylindrical shape having the outer diameter substantially equal to theinner diameter of the enlarged portion 1 a of the battery case 1. Asclearly shown in FIG. 8C, the insulation gasket 27 includes a holdinginner wall face 27 a having the inner diameter substantially equal tothe outer diameter of the filter portion 21 of the sealing member 8; asupporting bottom portion 27 b projecting inward from the lower end ofthe holding inner wall face 27 a at an angle; a guide tapered side 27 cthat broadens downward from a portion below the supporting bottomportion 27 b; and a latch projection 27 d that projects inward from theupper end of the holding inner wall face 27 a and has the inner diameterslightly smaller than the outer diameter of the filter portion 21. Theholding inner wall face 27 a, the supporting bottom portion 27 b, theguide tapered side 27 c, and the latch projection 27 d are formedintegrally. The projection length D of the supporting bottom portion 27b from the holding inner wall face 27 a is set in a range from 0.2 mm to0.4 mm, which allows the attachment of the insulation gasket 27 from oneside of the sealing member 8 that is an opposite side to the electrodeplate group 2. The detailed description of FIG. 8D will be describedlater.

The battery using the insulation gasket shown in FIGS. 8A through 8Dalso provides the same advantageous effects as those described in thefirst embodiment. More specifically, since the supporting ledge 1 b forsupporting the filter portion 21 of the sealing member 8 is formed tohorizontally fasten the battery case 1 in this battery, the annularsupporting portion 51 b formed by the annular groove 51 a in theconventional battery, as well as the ring-like upper insulation plate61, is eliminated. Thus, the upper end of the electrode plate group 2further extends toward the opening end of the battery case 1 by adistance provided by omission of the conventional annular supportingportion 51 b, thereby increasing the height of the electrode plate group2. In addition, the length of the positive lead 20 for electricallyconnecting the positive collector 11 and the filter portion 21,especially the length of the standing portion 20 b, is largely reduced.Therefore, the collecting distance in this battery is reduced by adistance corresponding to the reduction of the length of the positivelead 20, resulting in great reduction of the internal resistance of thebattery and increased output of the battery. Moreover, since the heightof the electrode plate group 2 is increased by the height correspondingto a useless space provided by the provision of the annular supportingportion 51 b in the conventional battery, the volume of the electrodeplate group 2 is increased. This increase of the volume increases thecapacity of the battery.

Moreover, the battery of the third embodiment has the followingadvantageous effect in addition to the advantageous effects that are thesame as those described in the first embodiment. Since the insulationgasket 27 has a shape that allows the attachment of the insulationgasket 27 to the sealing member 8 from the side opposite to theelectrode plate group 2, the insulation gasket 27 is mounted to thesealing member 8 that has been already welded to the positive lead 20.Thus, unlike a case where the sealing member bonded to the positive leaddrawn from the opening of the battery case is inserted into the batterycase while being rotated as in the conventional battery, it isunnecessary to bend the positive lead 20 in the manufacturing process ofthe battery. Thus, the positive lead 20 will be further shortened.

Next, the manufacturing process of the battery of the third embodimentwill be described with reference to FIGS. 9A through 11B. FIG. 9A showsa relative arrangement of the respective components to be assembled. Inthe first process, as shown with an arrow in FIG. 9A, the negativecollector 9 is brought into contact with the end 4 a (see FIG. 6) of thenegative electrode plate 4 of the electrode plate group 2 and is weldedto the end 4 a by resistance welding. In addition, the respectiveburring projections 18 a through 18 d of the positive collector 11 arebrought into contact with the end 3 a (see FIG. 6) of the positiveelectrode plate 3 of the electrode plate group 2 and are welded to theend 3 a by resistance welding. Further, the connection base portion 20 aof the positive lead 20 is positioned and arranged with respect to thepositive collector 11 in accordance with the relative arrangement shownin FIG. 7A, and thereafter the positive lead 20 is welded at twoportions to the positive collector 11. In this manner, the positive lead20 is connected to the positive electrode plate 3 with two weldedportions 28 a and 28 b and the positive collector 11. Thus, as shown inFIG. 9B, the attachment of the positive and negative collectors 11 and 9and the positive lead 20 to the electrode plate group 2 has beencompleted.

The resistance welding of the negative collector 9 and the positivecollector 11 mentioned above is performed by using a special welding jig(not shown). In a case of welding the positive collector 11 to the end 3a of the positive electrode plate 3, since each of eight burringprojections 18 a through 18 d extends in the radial direction of theelectrode plate group 2, the burring projections 18 a through 18 d areopposed to the positive electrode plate 3 at relative positions at whichthey intersect with the end 3 a of the positive electrode plate 3 atsubstantially right angles. Thus, by performing resistance welding foreach opening 14 while a pair of welding electrodes are brought intocontact with two flat portions on both sides of that opening 14 with apressure applied to the welding electrodes, a reactive current flowingin the surface of the positive collector 11 between the electrodes inthat pair is reduced because of the existence of the opening 14. On theother hand, welding currents flowing through the intersections of theburring projections 18 a through 18 d and the end 3 a of the positiveelectrode plate 3 are increased. Thus, the burring projections 18 athrough 18 d are melted while biting into the end 3 a of the positiveelectrode plate 3, and therefore the positive collector 11 is securelywelded to the end 3 a. In this manner, the electric resistances at thewelded portions at which the burring projections 18 a through 18 d arewelded to the end 3 a of the positive electrode plate 3 are reduced,thus reducing the internal resistance of the battery.

Subsequently, as shown in FIG. 10A, the connected portion 20 c of thepositive lead 20 and the peripheral edge portion of the filter portion21 of the sealing member 8 are bonded to each other by resistancewelding with the projections 24 shown in FIGS. 7A and 7B. The resistancewelding of the positive lead 20 and the filter portion 21 is possiblebecause it is performed when the insulation gasket 27 has not beenattached yet and before the assembly is inserted into the battery case1. More specifically, because the insulation gasket 27 has not beenattached and the assembly has not been inserted into the battery case 1,the resistance welding is performed via the projections 24 while onewelding electrode 29 is in contact with the lower surface of theconnected portion 20 c of the positive lead 20; the other weldingelectrode 30 is in contact with the upper surface of the peripheral edgeportion of the filter 21; and an insulation guide 31 is interposedbetween the peripheral end face of the filter portion 21 and the weldingelectrode 29.

Thus, the resistance welding mentioned above is performed stably withhigher precision so as to achieve excellent welding strength, ascompared with a case where the sealing member 54 arranged vertically iswelded to the positive lead 53, as shown in FIGS. 22 and 23. Moreover,one welding electrode 29 has an arc-like shape obtained by dividing theperipheral edge portion of the filter portion 21 into three portions,whereas the other welding electrode 30 has a ring-like shape. Thus, botha contact area between the welding electrode 29 and the connectedportion 20 c of the positive lead 20 and a contact area between theother welding electrode 30 and the peripheral edge portion of the filterportion 21 increase largely. Therefore, the other welding electrode 30receives a total load of the one welding electrode 29, the filterportion 21, and the connected portion 20 c of the positive lead 20 whilethe connected portion 20 c of the positive lead 20 and the filterportion 21 are surely in contact with each other under pressure. Thisallows the resistance welding to be performed more stably.

Then, as shown in FIG. 10B, the insulation gasket 27 is mounted to theperipheral edge portion of the filter portion 21 that has been bonded tothe positive lead 20 in the above-described manner. The insulationgasket 27 is pressed toward the peripheral edge portion of the filterportion 21 from the side of the filter portion 21, that is opposite tothe positive collector 11, i.e., from above, thereby the supportingbottom portion 27 b of the insulation gasket 27 made of nylon isdeformed and enlarged while the peripheral edge portion of the filterportion 21 slides on the guide tapered side 27 c. In this manner, theperipheral edge portion of the filter portion 21 is gradually insertedinto an internal space of the insulation gasket 27. At a time at whichthe lower end of the peripheral edge portion of the filter portion 21 iscoincident with a boundary between the supporting bottom portion 27 band the holding inner wall surface 27 a of the insulation gasket 27, asshown with chain double-dashed line in FIG. 8C, the insulation gasket 27is mounted to the filter portion 21 by interposing the peripheral edgeportion of the filter portion 21 from above and beneath with a restoringforce generated by deformation of the latch projection 27 d and thesupporting bottom portion 27 b in which their diameters are increased.

The length of the inward projection D of the supporting bottom portion27 b from the holding inner wall face 27 a may be set in a range from0.2 mm to 0.4 mm, as described above. In this case, in spite ofdifferences between types of batteries or material of the insulationgasket 27, it is possible to press and mount the insulation gasket 27 tothe filter portion 21 from above.

The electrode plate group 2 with the positive and negative collectors 11and 9, the positive lead 20, and the filter portion 21 mounted theretois inserted into the battery case 1, as shown in FIG. 10C. In thisstate, the insulation gasket 27 is placed on and supported by theannular supporting ledge 1 b of the battery case 1. Then, an elongatewelding electrode 32 is inserted into the circular hole at the center ofthe electrode plate group 2 from above through the vent opening 21 a ofthe filter portion 21 and the electrolyte-injection hole 13 of thepositive collector 11, and thereafter resistance welding is performedwhile the elastic connection portion 9 b of the negative collector 9 ispressed against the bottom of the battery case 1. Thus, the negativecollector 9 is welded to the bottom of the battery case 1.

Then, as shown in FIG. 11A, the opening end of the battery case 1 iscaulked inward, and thereafter the enlarged portion 1 a of the batterycase 1 is subjected to a process for reducing the diameter. In thisprocess, the diameter of the enlarged portion 1 a is reduced by pushingand inserting the battery case 1 into a cylinder for diameter reductionthat has a slightly smaller inner diameter than the outer diameter ofthe enlarged portion 1 a, from the bottom of the battery case 1. In thecaulking process, the caulked opening end of the battery case slightlypresses down the electrode plate group 2 via the filter portion 21, thepositive lead 20, and the positive collector 11.

In this manner, the electrode plate group 2 is vertically fastened so asnot to move in the direction of the axis of the battery case 1, i.e.,the vertical direction, so that it is secured while being compressed byabout 0.2 mm, for example. Thus, impact resistance and vibrationresistance are largely improved. Moreover, the insulation gasket 27 isdeformed by a pressing force applied from above by the opening end ofthe battery case 1 that has been caulked, so that the supporting bottomportion 27 b and the latch projection 27 d are pressed against the upperand lower surfaces of the peripheral edge portion of the filter portion21, respectively, as shown in FIG. 8D. On the other hand, the negativecollector 9 changes its shape by plastic deformation so as to flattenout the elastic connection portion 9 b because it receives a pressingforce applied by the electrode plate group 2, thereby the negativecollector 9 absorbs variations in heights of the ends 3 a and 4 a of thepositive and negative electrode plates 3 and 4. Furthermore, by reducingthe diameter of the enlarged portion 1 a of the battery case 1, thefilter portion 21 of the sealing member 8 is horizontally fastened withthe insulation gasket 27 interposed therebetween, so as to be secured bya significantly robust supporting structure.

Then, a predetermined amount of electrolyte is poured into the batterycase 1 that has been processed in a preliminary sealing processincluding caulking of the opening end of the battery case 1 and diameterreduction for the enlarged portion 1 a, from an injection nozzle 33through the vent opening 21 a of the filter portion 21 and theelectrolyte-injection hole 13 of the positive collector 11. Thisinjection process is performed in a stable state in which the filterportion 21 and the positive collector 11 are secured to the battery case1 connected to the electrode plate group 2, and therefore is performedsignificantly efficiently.

Finally, as shown in FIG. 11B, the filter portion 21 and the cap-shapedpositive terminal 22 of the sealing member 8 are welded to each otherwhile the cap-shaped positive terminal 22 is placed on the filterportion 21 with the safety vent body 23 interposed therebetween. Thus,assembly of the sealing member 8 has been completed, and this sealingmember 8 completely seals the opening of the battery case 1.

In the manufacturing method of the battery of the present embodiment, itis possible to mount the insulation gasket 27 to the filter portion 21that has been welded to the positive lead 20 by pressing the insulationgasket 27 against the filter portion 21 from above. Thus, the filterportion 21 and the positive lead 20 are bonded to each other byresistance welding significantly stably prior to the mounting of theinsulation gasket 27. This resistance welding can be performed withhigher precision so as to provide excellent welding condition, ascompared with a case in which the sealing member 54 arranged verticallyis welded to the positive lead 53, as shown in FIGS. 21A, 21B and 22,and a case of laser spot welding. Therefore, electric resistance at thewelded portion is reduced.

Moreover, the electrode plate group 2 to which the positive lead 20 andthe filter portion 21 of the sealing member 8 have been mounted inadvance is inserted into the battery case 1, and thereafter the sealingmember 8 is assembled by bonding the cap-shaped positive terminal 22 tothe filter portion 21 with the safety vent body 23 interposedtherebetween. Thus, it is not necessary to bend the positive lead 20 inthe manufacturing process of the battery, unlike the manufacturingprocess of the conventional battery in which the sealing member 54bonded to the positive lead 53 drawn out from the opening of the batterycase 51 is inserted into the battery case 1 while being rotated. Thatis, the positive lead 20 is shaped in advance to have the connectionbase portion 20 a, the standing portion 20 b, and the connected portion20 c. Therefore, as the positive lead 20, it is possible to use arelatively thick plate-like member. This further contributes toreduction of the internal resistance of the battery.

The synergistic effect that the positive lead 20 is shortened and madethicker and that the positive lead 20 and the filter portion 21 arewelded by resistance welding stably to provide good welding condition,achieves further reduction of the internal resistance of the battery, aswell as improvement of the battery characteristics, such as high-ratecharge-discharge characteristics.

In the manufacturing method described with reference to FIGS. 9A through11B, an example was described in which the positive collector 11 isbonded to the end 3 a of the positive electrode plate 3 and thereafterthe positive lead 20 is bonded to the positive collector 11. Thismanufacturing method may be modified in such a manner that the positivecollector 11 is bonded to the end 3 a of the positive electrode plate 3after the positive lead 20 is bonded to the positive collector 11. Inthis case, after the positive lead 20 shaped as shown in FIGS. 7A and 7Bis bonded to the positive collector 11, the positive lead 20 is bentperpendicularly at a portion near the welded portions 28 a and 28 b inthe connection base portion 20 a to stand vertically, thereby moving thepositive lead 20 upward so as not to disturb welding of the positivecollector 11 as shown in FIGS. 12A and 12B. After welding of thepositive collector 11 to the end 3 a of the positive electrode plate 3was completed, the positive lead 20 is bent to change its shape into theshape shown in FIG. 7B again. By employing the process mentioned above,welding of the positive collector 11 and the positive lead 20 isperformed more easily.

FIG. 13 is a vertical cross-sectional view of a sealing portion of abattery according to a fourth embodiment of the present invention, andFIGS. 14A and 14B are a plan view and a cross-sectional view,respectively, showing a relative arrangement of the positive collector11 and a positive lead 34 in the battery of the fourth embodiment. InFIGS. 13, 14A and 14B, the components that are the same as or similar tothose in FIGS. 6, 7A, and 7B are labeled with the same referencenumerals, thereby omitting redundant description. The battery of thefourth embodiment is different from that of the third embodiment in thatthe positive lead 20 in the third embodiment that has a shape in whichthe connected portion 20 c extends toward only one side of the positivecollector 11 is replaced with the positive lead 34 having a differentshape. The positive collector 11 is the same as that in the thirdembodiment. The positive lead 34 includes a connection base portion 34 ahaving a circular gas escape hole 34 d corresponding to theelectrolyte-injection hole 13 of the positive collector 11, a pair ofstanding portions 34 b respectively extending from both ends of theconnection base portion 34 a, and connected portions 34 c extending fromthe corresponding standing portions 34 b outward and parallel to theconnection base portion 34 a.

This battery provides the same advantageous effects as those mentionedin the third embodiment and further provides the following advantageouseffects. In a case of the positive lead 20 of the battery of the thirdembodiment, the current paths between two welded portions 28 a and 28 bat which the positive collector 11 and the positive lead 20 are weldedand three burring projections 18 a, 18 b, and 18 c are short, whereasthe current paths between the welded portions 28 a and 28 b and theother burring projection 18 d are long. On the other hand, in thepositive lead 34 of the battery of the present embodiment, four weldedportions 37 a through 37 d are provided for four burring projections 18a through 18 d, respectively, and the connected portions 34 c havingprojections 24 are provided near two of the welded portions 37 a through37 d. Thus, a current path between each of the four welded portions 37 athrough 37 d and an associated one of the four projections 24 is madeshort, thus improving collecting efficiency and further reducing theinternal resistance of the battery.

The battery of the present embodiment may be manufactured bymanufacturing processes similar to those shown in FIGS. 9A through 11B,with the same advantageous effects as those described in the thirdembodiment. However, the fabrication processes may be partially modifiedin such a manner that the positive lead 34 is bonded to the positivecollector 11 and thereafter the positive collector 11 is bonded to theend 3 a of the positive electrode plate 3. In this case, after thepositive lead 34 is bonded to the positive collector 11 in a relativearrangement shown in FIGS. 14A and 14B, the positive lead 34 is bentperpendicularly at portions near the welded portions 37 a through 37 darranged on both sides of the gas escape hole 34 d in the connectionbase portion 34 a so as to stand vertically, as shown in FIG. 14C. Thus,the portion other than the connection base portion 34 a of the positivelead 34 is moved upward so as not to disturb welding of the positivecollector 11 to the electrode plate group 2. After completion of thewelding of the positive collector 11 to the end 3 a of the positiveelectrode plate 3, the positive lead 34 is bent to change its shape intothe shape shown in FIGS. 14A and 14B again. By employing theseprocesses, the positive collector 11 and the positive lead 34 are weldedmore easily.

FIG. 15A is a partial cross-sectional view of another exemplaryinsulation gasket 38 according to the present invention. This insulationgasket 38 is a short cylindrical molded part formed of nylon having theouter diameter substantially equal to the inner diameter of the enlargedportion 1 a of the battery case 1. The insulation gasket 38 includes aholding inner wall face 38 a having the inner diameter substantiallyequal to the outer diameter of the filter portion 21 of the sealingmember 8; a supporting bottom portion 38 b projecting inward from thelower end of the holding inner wall face 38 a at an angle; a guidetapered side 38 c broadening downward from a portion below thesupporting bottom portion 38 b; a latch projection 38 d projectinginward from the upper end of the holding inner wall face 38 a and havingthe inner diameter slightly smaller than the outer diameter of thefilter portion 21; and a covering portion 38 e extending inward from thelatch projection 38 d at an angle. The holding inner wall face 38 a, thesupporting bottom portion 38 b, the guide tapered side 38 c, the latchprojection 38 d, and the covering portion 38 e are formed integrally.The projection length D of the supporting bottom portion 38 b from theholding inner wall face 38 a is set in a range from 0.2 mm to 0.4 mm.

In this insulation gasket 38, the projection length D of the supportingbottom portion 38 b from the holding inner wall face 38 a is set to fallwithin a range from 0.2 mm to 0.4 mm, as mentioned above. Thus, whenbeing pressed against the peripheral edge portion of the filter portion21 from above, the insulation gasket 38 is mounted to the peripheraledge portion of the filter portion 21 while interposing the peripheraledge portion from both sides in the vertical direction with an elasticforce generated by such a deformation of the latch projection 38 d andthe supporting bottom portion 38 b that they are enlarged, as shown withchain double-dashed line in FIG. 15A.

The covering portion 38 e of the insulation gasket 38 is shaped to beinclined inward, i.e., toward a direction in which the covering portion38 e is to be deformed when the opening end of the battery case 1 iscaulked inward. Thus, even if the length from the holding inner wallface 38 a is set longer than that in the insulation gasket 27 shown inFIGS. 8A through 8D, for example, the caulking of the opening end of thebattery case 1 is performed without any disturbance. For this reason,the length of the portion extending upward from the upper end of theholding inner wall face 38 a, including the latch projection 38 d andthe covering portion 38 e is set longer in this insulation gasket thanthat in insulation gaskets of existing batteries.

Therefore, as shown in FIG. 15B, when the opening end of the batterycase 1 is caulked inward, the covering portion 38 e of the insulationgasket 38, that extends longer, projects more inward than the openingend face 1 c of the battery case 1, so that the covering portion 38 eprevents contact of the opening end of the battery case 1 with the uppersurface of the filter portion 21 of the sealing member 8, as well asshort-circuit between them. On the other hand, in a typical battery, asshown in FIG. 8D, for example, the opening end face 1 c of the batterycase 1 projects more inward than the insulation gasket 27. Therefore,electrically conductive foreign particles may enter a space between theopening end of the battery case 1 and the filter portion 21 or theopening end of the battery case 1 may be deformed because of fall of thebattery or the like, resulting in short-circuit between the opening endof the battery case 1 and the filter portion 21.

FIGS. 16A through 16C illustrate still another exemplary insulationgasket 39 in the battery according to the present invention. FIG. 16A isa plan view, FIG. 16B is a cross-sectional view, and FIG. 16C is anenlarged view of a part of FIG. 16B. The insulation gasket 39 includes aholding inner wall face 39 a having the inner diameter substantiallyequal to the outer diameter of the filter portion 21 of the sealingmember 8, a supporting bottom portion 39 b projecting inward from thelower end of the holding inner wall face 39 a at an angle, a guidetapered side 39 c shaped to broaden downward from a portion below thesupporting bottom portion 39 b, and a covering portion 39 e projectingfrom the upper end of the holding inner wall face 39 a parallel to alower end face 39 d. The holding inner wall face 39 a, the supportingbottom portion 39 b, the guide tapered side 39 c, the lower end face 39d, and the covering portion 39 e are formed integrally. The projectionlength D of the supporting bottom portion 39 b from the holding innerwall face 39 a is set to fall within a range from 0.2 mm to 0.4 mm.

The insulation gasket 39 provides the same advantageous effects as thoseof the insulation gasket 38 shown in FIGS. 15A and 15B, and furtherprovides the following advantageous effects. In this insulation gasket39, the covering portion 39 e, that projects from the upper end of theholding inner face wall 39 a parallel to the lower end face 39 d, worksto be latched by the upper end portion of the filter portion 21, likethe latch projection 38 d in the insulation gasket 38 shown in FIGS. 15Aand 15B. Therefore, the latch projection 38 d will be omitted in thisinsulation gasket 39, thus simplifying the shape of the insulationgasket 39. Moreover, this insulation gasket 39 has an advantage that itsurely projects more inward than the opening end face 1 c of the batterycase 1 when caulking of the opening end of the battery case 1 isperformed.

The insulation gasket 27 in the batteries of the third and fourthembodiments, the insulation gasket 38 shown in FIGS. 15A and 15B, andthe insulation gasket 39 shown in FIGS. 16A and 16B have an advantagethat any of them is mounted to the peripheral edge portion of the filterportion 21 of the sealing member 8 from the side opposite to thepositive collector 11. In the mounting of the insulation gasket to thefilter portion 21, one side of the insulation gasket is laid over andattached to the peripheral edge portion of the filter portion 21, andthereafter the other side is laid over and attached to the peripheraledge portion of the filter portion 21 while being enlarged. Therefore,it is difficult to automate the mounting process of the insulationgasket to the filter portion 21 in a case of using any of theaforementioned insulation gaskets 27, 38, and 39.

Thus, by using an insulation gasket 40 shown in FIGS. 17A and 17B, themounting of the insulation gasket 40 to the filter portion 21 will beautomated. FIG. 17A is a partially broken cross-sectional view of theinsulation gasket 40. FIG. 17B is a partially broken cross-sectionalview showing a state where the peripheral edge portion of the filterportion 21 of the sealing member is securely held by the opening end ofthe battery case 1 that has been caulked inward with the insulationgasket 40 interposed between the filter portion 21 and the opening endof the battery case 1. Before mounting to the filter portion 21, theinsulation gasket 40 has a cross-sectional shape that broadens downward,i.e., toward a position at which the positive collector 11 is to bearranged when the insulation gasket 40 is mounted to the filter portion21, as shown in FIG. 17A. The insulation gasket 40 includes a holdinginner wall face 40 a that is to come into close contact with aperipheral end face of the filter portion 21 of the sealing member 8, asupporting bottom portion 40 b for supporting the peripheral edgeportion of the lower surface of the filter portion 21, and a coveringportion 40 c that is to be pressed against the peripheral edge portionof the upper surface of the filter portion 21. The holding inner wallportion 40 a, the supporting bottom portion 40 b, and the coveringportion 40 c are formed integrally.

FIGS. 18A through 18G are cross-sectional view sequentially showingmanufacturing processes of the battery using the above insulation gasket40. First, as shown in FIG. 18A, the insulation gasket 40 is supplied toa carrying-out station 41 formed by a pair of transfer rails and is thenpositioned at a predetermined take-out position. Thereafter, a transferjig 42 goes down from above and a spindle 43 of the transfer jig 42enters the inside of the insulation gasket 40 while deforming, i.e.,slightly enlarging the insulation gasket 40. Thus, the insulation gasket40 adheres to the outer circumferential surface of the spindle 43 by anelastic restoring force generated by the deformation. Then, when thetransfer jig 42 moves upward and away from the carrying-out station 41,the insulation gasket 40 adhering to the spindle 43 is taken away fromthe carrying-out station 41.

Subsequently, as shown in FIG. 18B, the transfer jig 42 with theinsulation gasket 40 moves to a position above the electrode plate group2 to which the positive collector 11, the positive lead 20, and thefilter portion 21 have been mounted in advance, and is then positionedand stopped at that position. Then, as shown in FIG. 18C, the transferjig 42 goes down and a center pin 45, which is caused to project fromthe spindle 43 by a force applied by a compression spring 44 in thetransfer jig 42, enters the inside of the electrolyte-injection hole 13positioned at the center of the filter portion 21 while compressing thespring 44. Thus, the insulation gasket 40 attached to the spindle 43 ispositioned at a predetermined relative position with respect to thefilter portion 21 by fitting of the center pin 45 and theelectrolyte-injection hole 13.

Then, as shown in FIG. 18D, a cylindrical holder 46, which fits aroundthe spindle 43 of the transfer jig 42 so as to be freely slidable on theouter circumferential surface of the spindle 43, goes down and the lowerend face of the holder 46 pushes the insulation gasket 40 down. Thus,the insulation gasket 40 is dismounted from the spindle 43, andthereafter is laid over the peripheral edge portion of the filterportion 21 as it is, because it has a cross-sectional shape thatbroadens downward. At this time, the spindle 43 is magnetized to absorbthe electrode plate group 2.

The transfer jig 42 that has adhered to the electrode plate group 2 bythe spindle 43 then moves to a position above the battery case 1 and ispositioned and stopped at that position, as shown in FIG. 18E. Then, thetransfer jig 42 goes down and inserts the electrode plate group 2 intothe battery case 1. During this process, a guide cylinder 47 is arrangedaround the opening end of the battery case 1. This guide cylinder 47 hasa shape in which the inner diameter is gradually reduced downward andthe smallest inner diameter is set to be substantially equal to theinner diameter of the enlarged portion 1 a of the battery case 1. Thus,as shown in FIG. 18F, when passing through the guide cylinder 47, theinsulation gasket 40 having the cross-sectional shape that broadensdownward is deformed to reduce the diameter of the lower part thereofwhile sliding on the inner circumferential surface of the guide cylinder47, so that the insulation gasket 40 is pushed to the enlarged portion 1a until it reaches a predetermined position in the enlarged portion 1 a.Then, the transfer jig 42 releases the magnetization of the spindle 43and moves up. When the guide cylinder 47 also has moved up, a stateshown in FIG. 18G is achieved. Then, when the cap-shaped positiveterminal 22 is mounted to the filter portion 21 with the safety ventbody 23 interposed therebetween, the assembly of the sealing member 8 isfinished. Finally, the opening end of the battery case 1 is caulkedinward and thereafter the enlarged portion 1 a is subjected to a processfor reducing its diameter. Thus, the battery is completed. According tothis manufacturing method, most of the processes will be automated.Therefore, it is possible to mass-produce the battery with highproductivity.

As is apparent from the above description, according to the battery ofthe present invention, a connection lead for electrically connecting thecollector and the sealing member is largely shortened, and thecollecting distance is also reduced by the length corresponding toreduction of the length of the connection lead. Moreover, internalresistance of the battery is greatly reduced, thereby increasing thebattery output. Furthermore, the height of the electrode plate group ismade higher by the height corresponding to a useless space provided bythe inclusion of the annular supporting portion in the conventionalbattery. Thus, the volume of the electrode plate group, as well as thecapacity of the battery, increases. Therefore, the battery of thepresent invention will be applicable to such as a power supply of acordless power tool or an electric vehicle, that require large loadcharacteristics. In addition, since the insulation gasket is mounted tothe filter portion of the sealing member by being pressed against thefilter portion from the side of the filter portion opposite to thecollector, the insulation gasket is mounted to the connection lead thathas been bonded to the collector in advance. Thus, the battery of thepresent invention is manufactured with high productivity.

Although the present invention has been fully described in connectionwith the preferred embodiment thereof, it is to be noted that variouschanges and modifications apparent to those skilled in the art are to beunderstood as included within the scope of the present invention asdefined by the appended claims unless they depart therefrom.

1. A method for manufacturing a battery comprising the steps of:accommodating a spiral electrode plate group in a cylindrical batterycase having a bottom, the battery case having an enlarged portion formedclose to an opening end thereof and an annular supporting ledge on aninner surface of a lower end of the enlarged portion, a collector of onepolarity being bonded to an upper end of the spiral electrode plategroup while a collector of another polarity is bonded to a lower endthereof; bonding one end of a connection lead to the collector of theone polarity in an arrangement in which a notch formed at the one end ofthe connection lead is in agreement with a part of a hole edge of anelectrolyte-injection hole at a center of the collector of the onepolarity, and then bending the connection lead at a portion near aportion bonded to the collector of the one polarity in such a mannerthat the connection lead stands vertically; bonding another end of thestanding connection lead to a portion of a sealing member arrangedparallel to the standing connection lead, the portion of the sealingmember being below a vent opening positioned at a center of the sealingmember; injecting electrolyte into the battery case through theelectrolyte-injection hole of the collector of the one polarity;rotating the sealing member while the connection lead is bent to form afolded portion between the one end and the other end thereof, insertingthe sealing member thus arranged into the opening of the battery case,and latching a peripheral edge portion of the sealing member on thesupporting ledge of the battery case with an insulation gasketinterposed therebetween; and fastening the peripheral edge portion ofthe sealing member in a horizontal direction with the insulation gasketinterposed therebetween by performing caulking of an opening end of thebattery case inward and reducing a diameter of the enlarged portion. 2.A battery comprising a cylindrical metal battery case having a bottomand an electrode plate group accommodated in the battery case, theelectrode plate group comprising a strip-shaped positive electrode plateand a strip-shaped negative electrode plate spirally wound with aseparator interposed therebetween, wherein an opening at an upper end ofthe battery case is sealed with a sealing member with an insulationgasket interposed therebetween, an enlarged portion is formed above anupper end of the electrode plate group on the side close to an openingend of the battery case, and an annular supporting ledge is formed on aninner surface of a lower end of the enlarged portion, a collector havingone polarity is bonded to an end of the electrode plate having the onepolarity that projects upward from the electrode plate group, one end ofa connection lead is bonded to the collector of the one polarity, andthe other end of the connection lead is bonded to a lower face of thesealing member, the insulation gasket is mounted to a peripheral edgeportion of the sealing member from a side opposite to the collector ofthe one polarity, the peripheral edge portion of the sealing member issupported by the supporting ledge with the insulation gasket interposedtherebetween, and the peripheral edge portion of the sealing member isfastened in a horizontal direction with the insulation gasket interposedtherebetween by performing caulking of the opening end of the batterycase inward and reducing a diameter of the enlarged portion.
 3. Thebattery according to claim 2, wherein the insulation gasket comprises aholding inner wall face with which a peripheral end face of the sealingmember is to fit; a supporting bottom portion, extending below theholding inner wall face, operable to support the peripheral edge portionof the sealing member from beneath; and a guide tapered face serving asan introduction port for mounting of the sealing member, the guidetapered face having a shape that broadens downward from the supportingbottom portion, wherein the holding inner wall face, the supportingbottom portion, and the guide tapered face are formed integrally.
 4. Thebattery according to claim 3, wherein a length of the supporting bottomportion projecting inward from the holding inner wall face is set in arange from 0.2 mm to 0.4 mm.
 5. The battery according to claim 3,wherein the insulation gasket comprises a covering portion formedintegrally therewith, the covering portion extending inward from anupper end of the holding inner wall face at an angle.
 6. The batteryaccording to claim 3, wherein the insulation gasket comprises a coveringportion formed integrally therewith, the covering portion extendinginward from an upper end of the holding inner wall face parallel to alower surface of the insulation gasket.
 7. The battery according toclaim 2, wherein the insulation gasket has a cross-sectional shape thatbroadens toward a position at which the collector is to be arranged whenthe insulation gasket is mounted on the sealing member, before theinsulation gasket is mounted to the peripheral edge portion of thesealing member.
 8. The battery according to claim 2, wherein theconnection lead is formed by a rectangular plate of electricallyconductive material, and comprises: a connection base portion bonded toa substantially central portion of the collector of one polarity beingextending outward; a standing portion be extending upward from theconnection base portion; and a connected portion, extending parallel tothe connection base portion from an upper end of the standing portiontoward a periphery of the sealing member, being bonded to a lowersurface of the sealing member.
 9. The battery according to claim 2,wherein the connection lead is formed by a rectangular plate ofelectrically conductive material, and comprises: a connection baseportion bonded to a substantially central portion of the collector ofone polarity and being extending outward; a pair of standing portions beextending upward from both ends of the connection base portion,respectively; and a pair of connected portions, extending parallel tothe connection base portion from upper ends of the pair of standingportions toward a periphery of the sealing member, respectively, beingbonded to a lower surface of the sealing member, respectively.
 10. Amethod for manufacturing a battery comprising the steps of: bonding acollector of one polarity and a collector of another polarity to upperand lower ends of an electrode plate group, respectively; bonding aconnection base portion of a connection lead to the collector of the onepolarity before or after the bonding of the collector of the onepolarity to the electrode plate group; bonding a connected portion ofthe connection lead to a lower surface of a peripheral edge portion of afilter portion of a sealing member by resistance welding, the connectedportion being formed continuously from the connection base portion witha standing portion interposed therebetween; mounting an insulationgasket to the peripheral edge portion of the filter portion from a sideopposite to the collector; accommodating the electrode plate group in acylindrical battery case having a bottom, and an enlarged portion closeto an opening end thereof and an annular supporting ledge formed on aninner surface of a lower end of the enlarged portion, and placing theperipheral edge portion of the filter portion on the supporting ledgewith the insulation gasket interposed therebetween; caulking the openingend of the battery case inward and reducing a diameter of the enlargedportion to horizontally fasten and secure the peripheral edge portion ofthe sealing member with the insulation gasket interposed therebetween;injecting electrolyte into the battery case through anelectrolyte-injection hole of the collector of the one polarity; andassembling the sealing member by bonding a cap terminal to the filterportion with a safety vent body interposed therebetween.
 11. The methodfor manufacturing a battery according to claim 10, wherein in welding ofthe connected portion of the connection lead to the peripheral edgeportion of the filter portion of the sealing member by resistancewelding, a current is applied across welding electrodes while one of thewelding electrodes, which has an arc-like shape corresponding to theperipheral edge portion of the filter portion, is brought into contactwith a lower surface of the connected portion and the other of thewelding electrodes, which has a ring-like shape, is brought into contactwith an upper surface of the peripheral edge portion of the filterportion.
 12. The method for manufacturing a battery according to claim10, wherein the insulation gasket having such a cross-sectional shapethat broadens toward a position at which the collector is to be arrangedwhen the insulation gasket is mounted on the sealing member, beforebeing mounted to the peripheral edge portion of the sealing member isused, the insulation gasket is laid over a bonded portion of the filterportion that has been bonded to the electrode plate group via thecollector and the connection lead in advance, from a side opposite tothe collector, and the insulation gasket and the electrode plate groupare inserted together into the battery case while the insulation gasketis deformed in such a manner that a portion thereof projecting outwardis pursed inward.